Hundreds of patients with a deadly heart condition are dying every year while stuck on an NHS waiting list amid long delays for life-saving treatment, research reveals.

About 300,000 people across the UK have aortic stenosis (AS), a serious but symptomless disease that weakens the heart’s aortic valve, which helps push blood around the body. Although AS is often fatal, patients survive and regain a normal life if it is detected and treated early.

Nevertheless, more than 400 people a year with AS die because they cannot get access fast enough on the NHS to a life-saving non-surgical procedure called transcatheter aortic valve implantation (Tavi), it has emerged.

The disclosure has come from a survey of Tavi waiting times at the 35 specialist centres across the UK that provide the procedure. Heart doctors say the findings have exposed an “unacceptable” mortality in Britain linked to the fact that it carries out far fewer Tavi procedures than many other European countries.

Dr Jon Byrne, a cardiologist at King’s College hospital in London, who initiated the research, said: “Of all the people on the waiting list to have Tavi, 8% died before they received treatment – 8% is a big figure. That 8% is just over 400 patients a year.

“It’s disturbing that this is happening. While some of those waiting die of other conditions, a significant proportion of them would have survived if they had been treated with Tavi.”

The true death toll is much higher – probably about 800 a year, Byrne said – because the survey only received data from 18 of the 35 centres. AS mainly affects people in their 70s, 80s and 90s.

The research, by the medical group Valve for Life, also found that:

• A death rate as high as 20% at some hospitals which perform Tavi.

• The average waiting time for the procedure across the UK is 142 days – over 20 weeks – even though those with severe AS have a 50% risk of dying.

• White patients are more likely to undergo Tavi than those from minority ethnic communities.

In an article for the website Cardiology News that will be published on Monday, Byrne writes: “These findings expose a growing crisis in access to Tavi across the UK.

“Despite the dedication and expertise of clinicians delivering exceptional care under increasing pressure, system inefficiencies, health inequalities and capacity constraints continue to put patients at risk.”

The long waiting times for patients between being referred for Tavi and having it “are leaving thousands of patients at risk”, Byrne writes, in an opinion piece co-authored with Wil Woan, the executive director of the charity Heart Valve Voice.

Woan said: “Evidence collected by the European Society of Cardiology shows that the UK is well behind Europe in the amount of TAVI we do. It means that lots of people are dying unnecessarily.

“TAVI gives people with AS their life back. It makes them fitter, stronger and healthier. The NHS needs to expand the number of people who have it.”

NHS England is understood to be developing plans to tackle mortality through a fast-track process under which the most urgent AS cases will undergo Tavi within eight weeks.

Delays in accessing Tavi also put “a significant strain on the NHS” because patients who go untreated end up needing to be admitted to hospital as emergencies, the authors add.

Dr Sonya Babu-Narayan, the British Heart Foundation’s clinical director, said: “It’s concerning to hear red flags raised about patients dying whilst waiting in situations in which a timely heart procedure may have saved their life.

“Nearly four out of 10 people are waiting more than 18 weeks [for treatment], which is too long when it comes to heart conditions, where timely care is critical.

“Long delays at this scale put people at risk of living in ill health or being unable to work due to heart failure which could have been avoided, and having their lives cut short.”

The Department of Health and Social Care acknowledged that heart patients were facing long delays.

A spokesperson for the department said: “Because of the dire state of the NHS this government inherited, patients around the country, including those suffering from aortic stenosis, are waiting too long for treatment.

“Through our plan for change, we are delivering the investment and reform needed to get the NHS back on its feet and provide faster treatment for everyone who needs it, including those waiting for Tavi.”

Meanwhile, growing numbers of people in the UK under 65 are dying of heart attacks and strokes, reversing decades of progress on cardiac disease, the British Heart Foundation warned on Monday.

The rate of people aged 20-64 dying of heart problems rose from 49 per 100,000 in 2019 to 55 per 100,000 in 2023, analysis by the charity shows. Deaths from cardiac disease among working age adults rose by 18% over the same period, from 18,693 in 2019 to 21,975 in 2023 – 420 a week.

The increasingly unhealthy population, health inequalities, obesity and Covid-19 are among the factors that explain the upward trend, the BHF said.